Abstract
Low-birthweight (LBW; <2,500 g) babies are at a higher risk of poor educational achievement, disability, and metabolic diseases than normal-birthweight babies in the future. However, reliable data on factors that contribute to LBW have not been considered previously. Therefore, we aimed to examine the distribution of the causes for LBW. A retrospective review of cases involving 4,224 babies whose mothers underwent perinatal care at Keio University Hospital between 2013 and 2019 was conducted. The LBW incidence was 24% (1,028 babies). Of the 1,028 LBW babies, 231 babies were from multiple pregnancies. Of the 797 singleton LBW babies, 518 (65%) were born preterm. Obstetric complications in women with preterm LBW babies included premature rupture of membrane or labor onset (31%), hypertensive disorders of pregnancy (HDP, 64%), fetal growth restriction (24%), non-reassuring fetal status (14%), and placental previa/vasa previa (8%). Of the 279 term LBW babies, 109 (39%) were small for gestational age. Multiple logistic regression analyses revealed the following factors as LBW risk factors in term neonates: low pre-pregnancy maternal weight, inadequate gestational weight gain, birth at 37 gestational weeks, HDP, anemia during pregnancy, female sex, and neonatal congenital anomalies. HDP was an LBW risk factor not only in preterm births but also in term births. Our results suggest that both modifiable and non-modifiable factors are causes for LBW. It may be appropriate to consider a heterogeneous rather than a simple classification of LBW and to evaluate future health risks based on contributing factors.
Highlights
Low birthweight (LBW) is defined as a birthweight < 2,500 g, and the proportion of neonates identified as having LBW during the past decade is reported to be approximately 10% in Japan
There were 276 babies born from multiple pregnancies and 22.5% of the babies with LBW were from multiple pregnancies
The association between LBW and future health problems among preterm infants was analyzed in several previous articles, but these studies did not address the causes for preterm birth [1,18], and other reports regarding the causes for LBW did not even mention the gestational weeks at birth [2,3,5]
Summary
Low birthweight (LBW) is defined as a birthweight < 2,500 g, and the proportion of neonates identified as having LBW during the past decade is reported to be approximately 10% in Japan. Neonates with LBW at delivery are known to have a higher risk of infant morbidity and mortality and poor educational achievement, disability, and the development of metabolic diseases (i.e., type 2 diabetes, cardiovascular disease, and hypertension) in the future [1,2,3,4]. A recent report has indicated that LBW is associated with an increased risk of type 2 diabetes in Japanese adults [5]. Normile D (2018) raised concerns regarding the future of Japanese healthcare in relation to the increasing number of neonates with LBW [6].
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